Cherry blossom is three weeks of it. Flip through the other forty-nine — and watch what's in bloom move up and down the country.
The calendar is the way in. Underneath it sits the ordinary thing — search, filter by month or flower, and open any of the 412 spots.

Photo Koda6029 (CC BY-SA 4.0) — via Wikimedia Commons
About a million cosmos of some 50 kinds, plus 20,000 dahlias, on the ski slopes below Mount Kurohime. Open from late July to mid October.